The typical bearing for a railcar fits around a journal at the end of an axle where it is captured between a backing ring and an end cap. The backing ring seats against a fillet that merges into an enlarged dust guard section, while the end cap fits over the end of the journal to which it is secured with cap screws. On most journals seal wear rings fit between the bearing and the backing ring and also between the bearing and the end cap. Seals encircle the wear rings and exclude contaminants from the bearing. When tightened, the cap screws bear down against the end cap and clamp the bearing securely between the backing ring and end cap. This forces the backing ring snugly against the fillet.
The journals on any railcar axle represent the regions of least diameter in the axle, yet it is through these journals and nearby dust guard sections, which are somewhat larger, that the weight of the railcar is transferred to the wheels. Being subject to considerable weight, the journals flex cyclically as wheels roll along the rails of a railroad track, with most of the flexure occurring near the small ends of the fillets. The flexure produces movement between the backing rings and the fillets, and as a consequence both experience fretting and wear. When water seeps into the spaces between the backing rings and the fillets, it exacerbates the fretting with corrosion. The movement produces more wear where the seal wear rings that lie between the backing rings and the bearings abut races of the bearings. Sometimes the wear at a journal and wear ring is enough to eliminate the clamp fit that holds the bearing in place, and this disturbs the setting for the bearing, imparting more end play than desired.
To combat fretting wear and corrosion at axle fillets, bearing manufacturers introduced the fitted backing ring. It had a counterbore that snugly received the dust guard section adjacent to the fillet. Moreover, the American Association of Railroads (AAR) set standards for the fitted backing rings and further specified tolerances for the diameters of dust guard sections so that interference fits would exist between the dust guard sections and the counterbores of the backing rings. Thus, a fitted backing ring required the application of some force during the last increment of installation to overcome the interference fit. The interference fit stiffened the joint between the backing ring and the fillet on the journal and excluded moisture, thus reducing both fretting and corrosion between the backing ring and the journal. However, the AAR specified dust guard sections of larger diameter for the new axles, that is to say, dust guard diameters larger than those on older traditional axles. This enabled the new fitted backing rings to be used interchangeably with the older traditional axles and the new axles, but without interference fits on the older axles. In the absence of an interference fit, a fitted backing ring possesses little, if any, advantage over a more traditional backing ring without a counterbore for receiving the dust guard section. Moreover, fitted backing rings and likewise the dust guard sections over which they fit required additional machining to close tolerances which increases the expense for manufacturing them.
In order to rigidify the new backing rings on old traditional axles, railroads began installing compressible stabilizing rings in the counterbores of so-called fitted backing rings and around the dust guard sections of the traditional axles. The typical stabilizing ring took the form of a stainless steel tube of circular configuration. It occupied the space between the lip on the backing ring and the dust guard section of the traditional axle in a state of compression and hence stabilized the backing ring over a fillet leading up to the dust guard section. See U.S. Pat. No. 7,219,938, FIGS. 1-3. Those stabilizing rings are difficult to form in a circular configuration and are otherwise expensive to manufacture.